Weather precautions
The dome must be closed when
- outside humidity reaches 90%, OR
- the mirror temperature approaches within 2 degrees of the dew-point, OR
- the wind speed gusts for more than 10 sec above 80km/hr, OR
- the wetness alarm goes off.
All these alarms are indicated on the Casella MET display. In case of an
alarm the field with the concerned value will turn red and the system will
start beeping. This can be silenced by typing `A' on the PC's keyboard.
Mostly you will have to close the dome due to high humidity
To give you early warning about rising humidity, an additional alarm will
sound from the MET receiver box:
- Pointing left you will be warned if humidity rises over 75%,
- pointing right the alarm will sound with humidity >= 90%.
- In the middle position the alarm is muted.
n.b. Remember to re-activate this alarm before re-opening the dome!
The dome can be reopened when humidity has dropped below 80% and no other
alarm (dew-point, wind, wet) is present anymore.
If there is ICE on the dome
- The telescope log book will tell you if it's OK to open the dome.
- If in doubt ask the DE/IO.
- If the shutter shows any resistance to movement (watch it while opening),
don't force it.
- Always wear a hard hat when on the roof, never ever try to chip ice free
on dome or shutter!
How th close dome quickly
- First close the primary mirror cover.
- Then switch the TCS to engineering mode: press the button 'COMP/ENG'
(the telescope control will start beeping, acknowledge with
USER>ack) OR simply type USER>eng.
- Close the dome. Bring the lower shutter down first: press 'lower micro'
while in 'main over travel', otherwise 'lower main'.
- Now bring the upper shutter down using the same technique.
Observing at low elevation
If you want to observe at a zenith distance between 57 and 70 degrees
(33-20 degrees elevation) then you need to rise the lower shutter.
There won't be any warning from the telescope control, so you will have to
check the ZD from time to time.
- Push the yellow button under "SELECT MANUAL CONTROL", labeled
"DOME SHUTRS" to get the control of the shutters.
- On the engineering rack, under "LOWER SHUTTER", push the "RAISE MICRO"
button until the "MAIN OVER TRAVEL" light underneath goes off.
- Push the "RAISE MAIN" button on the side of the previous; while rising
you hear two bangs caused by the segments of the shutter catching the next,
keep the button pressed until you hear the motor stop. It takes
approximately 30 seconds.
- * Undo * the "DOME SHUTRS" button, otherwise the dome wont track the
object anymore.
You can now observe below 33 degrees elevation.
Remember to lower the shutter again when you go to a new source above 33
degrees elevation.
To do this:
- Select manual control as before with the "DOME SHUTRS" button.
- With "LOWER MAIN" bring the shutter down as far as it goes.
- With "LOWER MICRO" fully lower the shutter, keep the button pressed
some 10 seconds to be sure.
- Undo the "DOME SHUTRS" button.
Note that if you don't lower the bottom shutter completely the upper
shutter won't seal the dome at the top, so with rain and wind water
will penetrate into the dome.
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